Mariah (1990)

Mariah (there never was an xVAX name) was an intermediate step between Rigel
and NVAX. Mostly a conversion of Rigel into CMOS3, it included two
new features: a redesigned cache chip that supported write back caching,
and support for the (new at the time) 32b physical memory ECO.

Starting with Mariah, my information on the microprocessor chips becomes
less detailed.

The Mariah cache controller supported up to 256KB of write through or
write back cache.

Mariah shipped in 1990 as an upgrade to VAX workstations and to the mid-range
VAX 6000 series. The low-end system group (VAX 4000) chose to skip
Mariah and go directly to NVAX.

Personal Narrative

While Mariah started on my watch as manager of the Microprocessor Group,
it finished under my successor's (Dan Casaletto). Mariah was intended to
stretch the life-time of the VAX 6000 by supporting write-back instead of
write-through caching, which would ease the burden on the main memory bus
(the XMI).

Mariah had a companion Advanced Development project, Mistral. The goal
of Mistral was to build a much higher speed version of Mariah by cooling
the chip-set to liquid nitrogen temperatures. The A/D team did pioneering
work on the process and system implications of super-cooling, only to find
that simply waiting for the next-generation chip produced an equivalent system
solution as quickly at lower investment.